The fibers that extend through the walls of the ventricles and allow the rapid, immediate spread of the impulse throughout the ventricular myocardium are called fibers.

The Purkinje fibers are the fibers responsible for spreading impulses to both the left and right ventricular myocardium of the heart. These fibers extend through parts of the heart immediately spreading impulses for the heart to contract allowing the right amount of blood to flow within the ventricles.